Impact of A-Site Sr Substitution in LaFeO3 on Syngas Selectivity During Chemical Looping Dry Reforming of Methane (CL-DRM).

La1-xSrxFeO3 (0 ≤ x ≤ 1) perovskite oxygen carriers (OCs) were evaluated for dry reforming of methane (DRM) at 900°C under co-feed and chemical-looping (CL-DRM) configurations. Sr substitution decreased CH4/CO2 conversions in co-feed DRM, indicating suppressed intrinsic catalytic activity. In contrast, CL-DRM enhanced CH4 conversion by LaFeO3 to ∼75%-79% but promoted carbon deposition and a deviation of the H2/CO ratio from 2 (2.6). Sr-containing compositions exhibited lower CH4 conversion but improved carbon balance and syngas selectivity. La0.7Sr0.3FeO3 provided the best compromise, achieving ∼40% CH4 conversion, an ideal H2/CO ratio of 2, and a carbon balance above 95%. Sr2+ substitution induces Fe4+/Fe3+ charge compensation and modifies the oxygen-defect environment. The improved coke resistance is primarily associated with the suppression of nonselective CH4 cracking rather than with enhanced oxygen mobility. These findings establish that selective and stable syngas production in CL-DRM is governed not by maximizing oxygen reactivity, but by precisely balancing oxygen exchange kinetics with methane activation.